US20070120557A1 - Signal processing circuit for encoder - Google Patents

Signal processing circuit for encoder Download PDF

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Publication number
US20070120557A1
US20070120557A1 US11/564,178 US56417806A US2007120557A1 US 20070120557 A1 US20070120557 A1 US 20070120557A1 US 56417806 A US56417806 A US 56417806A US 2007120557 A1 US2007120557 A1 US 2007120557A1
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detectors
difference
angular
calculating
angular values
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US7619537B2 (en
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Mitsuyuki Taniguchi
Hirofumi Kikuchi
Tadayoshi Matsuo
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Fanuc Corp
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Fanuc Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/24457—Failure detection
    • G01D5/24461—Failure detection by redundancy or plausibility
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D18/00—Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
    • G01D18/001—Calibrating encoders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/24471—Error correction
    • G01D5/2449—Error correction using hard-stored calibration data

Definitions

  • the present invention relates to a signal processing circuit for an encoder of a type having two detectors arranged on both sides of a rotating shaft in order to eliminate an eccentricity error.
  • One of the detection errors that can occur in an encoder is an eccentricity error, i.e., the error caused by the eccentricity of its rotating part.
  • This eccentricity error can be canceled by arranging two detectors on both sides of the rotating shaft and by taking an average between the angular values ⁇ 1 and ⁇ 2 calculated from their respective output signals, as described, for example, in the prior art section of JP 3195117B.
  • the difference between ⁇ 1 and ⁇ 2 calculated from the output signals of the respective detectors may become equal to 180°, depending on the mounting condition of the detectors; in that case, two solutions ⁇ ′ and ⁇ ′′ can occur, resulting in a 180° displacement, as shown in FIG. 3 .
  • the detectors have had to be mounted by exercising care so that the difference between ⁇ 1 and ⁇ 2 will not become equal to 180° while considering the positional relationship between the detectors, and hence the problem that it takes time to mount the detectors appears.
  • an encoder signal processing circuit for calculating position data by processing signals output from first and second detectors arranged on both sides of a rotating shaft, comprising: angular value calculating means for calculating first and second angular values respectively from the output signals of the first and second detectors; initial difference storing means for storing an initial value of an angular difference calculated between the first and second angular values; correcting means for correcting one or the other of the first and second angular values by the initial value of the angular difference stored in the initial difference storing means; and position data calculating means for calculating the position data by taking an average between the two angular values after the correction is made by the correcting means.
  • the two angular values after the correction become close to each other; as a result, if the detectors are mounted in any positional relationship, the situation where the difference between the two values becomes equal to 180°, causing two solutions to occur, can be prevented, and thus the mounting of the detectors can be facilitated.
  • FIG. 1 is a diagram for explaining the averaging of angular values
  • FIG. 2 is a diagram for explaining the averaging of angular values
  • FIG. 3 is a diagram for explaining the problem of averaging that can occur when the angular difference is 180°;
  • FIG. 4 is a block diagram showing a first embodiment of the present invention.
  • FIG. 5 is a block diagram showing a first embodiment of the present invention.
  • FIG. 4 is a block diagram showing the configuration of an encoder signal processing circuit according to a first embodiment of the present invention.
  • an analog section 10 As a rotating part 12 rotates, two sine wave signals A 1 and B 1 , 90° apart in phase, are output from a detector 14 mounted near the rotating part 12 . Similarly, sine wave signals A 2 and B 2 are output from a detector 16 mounted opposite the detector 14 across the rotating part 12 .
  • Analog/digital converters 20 and 22 each interfacing the analog section 10 with a digital section 18 , convert the analog values A 1 , B 1 , A 2 , and B 2 into digital values A 1D , B 1D , A 2D , and B 2D , respectively.
  • An interpolation circuit 24 calculates an angular value ⁇ 1 from the digital values A 1D and B 1D by a known method, and outputs the result.
  • an interpolation circuit 26 calculates an angular value ⁇ 2 from the digital values A 2D and B 2D , and outputs the result.
  • the value of ⁇ may be measured a plurality of times, and its average value may be stored as ⁇ .
  • FIG. 5 shows a second embodiment according to the present invention.
  • an alarm processor 36 is added to the configuration of FIG. 4 .
  • the alarm processor 36 outputs an alarm when 180° ⁇ ALM ⁇ 3 ⁇ 2 ⁇ 180°+ ⁇ ALM , that is, when the angular difference ( ⁇ 3 ⁇ 2 ) after the correction lies within the range of 180° to ⁇ ALM , where ⁇ ALM is a predetermined value.
  • an alarm can be issued whenever there arises the possibility of an abnormal value being output as the phase difference after the correction becomes close to 180° due, for example, to the breakage or a displacement in the mounting position of the detectors.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)

Abstract

In an encoder which is equipped with two detectors arranged on both sides of a rotating shaft in order to eliminate an eccentricity error, the mounting of the detectors is facilitated by making provisions so as to not cause a problem in the calculating of an average even if the detectors happen to be so mounted that the difference between the angular values calculated from the outputs of the respective detectors becomes equal to 180°. In an initialization process after power on, the difference Δθ between the angular values θ1 and θ2 calculated from the signals output from the respective detectors is stored as an initial value. Position data θ is output by taking an average between θ3 and θ2, where θ3 is a value obtained by correcting θ1 by the initial difference Δθ.

Description

    BACKGROUND OF THE INVENTION
  • 1. Field of the Invention
  • The present invention relates to a signal processing circuit for an encoder of a type having two detectors arranged on both sides of a rotating shaft in order to eliminate an eccentricity error.
  • 2. Description of the Related Art
  • One of the detection errors that can occur in an encoder is an eccentricity error, i.e., the error caused by the eccentricity of its rotating part. This eccentricity error can be canceled by arranging two detectors on both sides of the rotating shaft and by taking an average between the angular values θ1 and θ2 calculated from their respective output signals, as described, for example, in the prior art section of JP 3195117B.
  • As the average θ=(θ3+θ2)/2 is the average of angular values, it is not the mere average of the values, but the value of θ is chosen so that, after the averaging, the angle θ is located between θ1 and θ2, as shown in FIGS. 1 and 2.
  • However, in a certain type of encoder, such as a magnetic encoder, in which the detectors are mounted to the stator or rotor after the encoder is assembled, the difference between θ1 and θ2 calculated from the output signals of the respective detectors may become equal to 180°, depending on the mounting condition of the detectors; in that case, two solutions θ′ and θ″ can occur, resulting in a 180° displacement, as shown in FIG. 3.
  • Therefore, to avoid the above situation, in the prior art the detectors have had to be mounted by exercising care so that the difference between θ1 and θ2 will not become equal to 180° while considering the positional relationship between the detectors, and hence the problem that it takes time to mount the detectors appears.
    • SUMMARY OF THE INVENTION
  • It is accordingly an object of the present invention to provide a signal processing circuit that facilitates the mounting of the detectors in an encoder of the type in which two detectors are arranged on both sides of the rotating shaft in order to eliminate an eccentricity error.
  • According to the present invention, there is provided an encoder signal processing circuit, for calculating position data by processing signals output from first and second detectors arranged on both sides of a rotating shaft, comprising: angular value calculating means for calculating first and second angular values respectively from the output signals of the first and second detectors; initial difference storing means for storing an initial value of an angular difference calculated between the first and second angular values; correcting means for correcting one or the other of the first and second angular values by the initial value of the angular difference stored in the initial difference storing means; and position data calculating means for calculating the position data by taking an average between the two angular values after the correction is made by the correcting means.
  • When one or the other of the first and second angular values is corrected by the initial value of their difference, if the angular value before the correction contains an error associated with the positional relationship between the detectors, the two angular values after the correction become close to each other; as a result, if the detectors are mounted in any positional relationship, the situation where the difference between the two values becomes equal to 180°, causing two solutions to occur, can be prevented, and thus the mounting of the detectors can be facilitated.
    • BRIEF DESCRIPTION OF THE DRAWING
  • FIG. 1 is a diagram for explaining the averaging of angular values;
  • FIG. 2 is a diagram for explaining the averaging of angular values;
  • FIG. 3 is a diagram for explaining the problem of averaging that can occur when the angular difference is 180°;
  • FIG. 4 is a block diagram showing a first embodiment of the present invention; and
  • FIG. 5 is a block diagram showing a first embodiment of the present invention.
    • DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • FIG. 4 is a block diagram showing the configuration of an encoder signal processing circuit according to a first embodiment of the present invention.
  • In an analog section 10, as a rotating part 12 rotates, two sine wave signals A1 and B1, 90° apart in phase, are output from a detector 14 mounted near the rotating part 12. Similarly, sine wave signals A2 and B2 are output from a detector 16 mounted opposite the detector 14 across the rotating part 12. Analog/ digital converters 20 and 22, each interfacing the analog section 10 with a digital section 18, convert the analog values A1, B1, A2, and B2 into digital values A1D, B1D, A2D, and B2D, respectively. An interpolation circuit 24 calculates an angular value θ1 from the digital values A1D and B1D by a known method, and outputs the result. Similarly, an interpolation circuit 26 calculates an angular value θ2 from the digital values A2D and B2D, and outputs the result.
  • A Δθ calculator 28 calculates Δθ=θ2−θ1 (or θ1−θ2), and stores the value of Δθ in a memory 30 after mounting the detectors 14 and 16 and before initiating the operation of the encoder or in the initialization process after power on. Here, the value of Δθ may be measured a plurality of times, and its average value may be stored as Δθ. A corrector 32 applies a correction by adding the value of Δθ stored in the memory 30 to the value of θ1 (or θ2), i.e., by the calculation of θ3=θ1+Δθ.
  • A position data calculator 34 calculates the average between the corrected value θ3 and the value of θ2, i.e., θ=(θ3+θ2)/2, and outputs the result as the position data θ.
  • In this way, by applying a correction by adding the initial difference Δθ to the angular value θ1, the initial phase difference associated with the positional relationship between the detectors 14 and 16 can be canceled, and the situation where the difference between θ1 and θ2 becomes equal to 18020 can thus be avoided. That is, when mounting the detectors 14 and 16, there is no need to exercise care so that the difference between the angular values calculated from the respective output signals will not become equal to 180°.
  • FIG. 5 shows a second embodiment according to the present invention. In this embodiment, an alarm processor 36 is added to the configuration of FIG. 4. The alarm processor 36 outputs an alarm when 180°−θALM<θ3−θ2<180°+θALM, that is, when the angular difference (θ3−θ2) after the correction lies within the range of 180° to θALM, where θALM is a predetermined value.
  • In this way, an alarm can be issued whenever there arises the possibility of an abnormal value being output as the phase difference after the correction becomes close to 180° due, for example, to the breakage or a displacement in the mounting position of the detectors.

Claims (2)

1. An encoder signal processing circuit for calculating position data by processing signals output from first and second detectors arranged on both sides of a rotating shaft, comprising:
angular value calculating means for calculating first and second angular values respectively from the output signals of the first and second detectors;
initial difference stoning means for storing an initial value of an angular difference calculated between the first and second angular values;
correcting means for correcting one of the first and second angular values by the initial value of the angular difference stored in the initial difference storing means; and
position data calculating means for calculating the position data by taking an average between the two angular values after the correction is made by the correcting means.
2. An encoder signal processing circuit according to claim 1, further comprising alarm outputting means for outputting an alarm when the difference between the two angular values, after the correction is made by the correcting means, lies within a prescribed range.
US11/564,178 2005-11-29 2006-11-28 Signal processing circuit for encoder Active 2027-10-31 US7619537B2 (en)

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JP2005343478A JP4005096B2 (en) 2005-11-29 2005-11-29 Encoder signal processing circuit
JP2005343478 2005-11-29

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US20180088187A1 (en) * 2016-09-29 2018-03-29 Aisin Seiki Kabushiki Kaisha Magnetic sensor and magnetic sensor system
CN111146979A (en) * 2018-11-02 2020-05-12 宝沃汽车（中国）有限公司 Initial angle correction method and device of motor rotor and electric vehicle

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EP2176626A4 (en) * 2007-08-08 2011-03-30 Eliezer Zeichner Encoding device, system and method
US8179127B2 (en) * 2007-11-06 2012-05-15 GM Global Technology Operations LLC Method and apparatus to monitor position of a rotatable shaft
WO2011125357A1 (en) 2010-04-02 2011-10-13 株式会社安川電機 Encoder, drive device, absolute position calculation method, and encoder manufacturing method
CN102169721A (en) * 2010-12-16 2011-08-31 中国兵器工业第二0六研究所 Software self-calibrating method for position codes
CN102806494B (en) * 2011-05-31 2016-03-02 德马吉森精机株式会社 Rotation angle location device
JP5948023B2 (en) * 2011-07-08 2016-07-06 オークマ株式会社 Absolute position detector with abnormality detection function
CN105910629B (en) * 2014-05-06 2018-01-12 盛铂科技（上海）有限公司 A kind of rotary encoder biphase signaling process circuit and its signal processing method
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JP2018059714A (en) * 2016-09-30 2018-04-12 キヤノン株式会社 Eccentricity calculation method, rotary encoder, robot arm and robot apparatus
CN106482669B (en) * 2016-11-29 2018-10-26 中国科学院长春光学精密机械与物理研究所 A kind of angle displacement measurement system using twin-line array image detector
CN110959101B (en) * 2017-07-27 2023-01-17 株式会社尼康 Correcting device, encoder device and manufacturing method thereof
CN108426599A (en) * 2018-03-09 2018-08-21 浙江赛安电气科技有限公司 A kind of magnetic coder trouble hunting method
TWI730564B (en) 2019-12-26 2021-06-11 財團法人工業技術研究院 Encoder and signal processing method using the same
CN117949021A (en) * 2024-03-26 2024-04-30 横川机器人（深圳）有限公司 Implementation method of double-sensing photoelectric angle encoder, encoder and medium

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CN111146979A (en) * 2018-11-02 2020-05-12 宝沃汽车（中国）有限公司 Initial angle correction method and device of motor rotor and electric vehicle

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Publication number Publication date
JP4005096B2 (en) 2007-11-07
US7619537B2 (en) 2009-11-17
JP2007147488A (en) 2007-06-14
CN1975336B (en) 2010-05-12
CN1975336A (en) 2007-06-06
EP1790951B1 (en) 2014-11-26
EP1790951A1 (en) 2007-05-30

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